Batteries such as lithium ion batteries are widely used due to their small volume, high energy density, non-pollution, etc. Active materials in the battery need to be activated by a pre-charging process (also known as a transformation process), before the battery can work normally. In the transformation process, gas may be generated inside the battery. In the existing transformation process, the gas sometimes cannot be successfully discharged from the interior of the battery, or the moisture in the environmental air may be brought into the battery, causing the moisture content of the electrolyte to be over a certain limit. If the gas generated in the transformation process cannot be discharged successfully from the battery, gas expansion will occur. Gas expansion in the battery may seriously affect the properties and operation of the battery. Thus, in the transformation process, whether the gas generated inside the battery can be discharged successfully via a sealing structure of an injection hole has a great influence in the performance of the battery.